This is a guide on how to install mFi Controller, for anyone still using it. mFi has not received security updates since 2016.
If you are looking for an mFi replacement, Ubiquiti is developing new products in this space including UniFi LED and UniFi SmartPower.
1. Download Debian 7 netinst CD image: https://www.debian.org/releases/wheezy/debian-installer/
2. Install
3. On the "Configure the package manager" step, rather than selecting a nearby country, scroll to the top and select "enter information manually"
4. Enter "archive.debian.org" as the mirror hostname
5. You will receive an error that there won't be any security updates from Debian
6. Once the installation is complete, log in as root or use su to become root, then run these commands to install mFi Controller:
apt-get update -y
echo "deb http://dl.ubnt.com/mfi/distros/deb/ubuntu ubuntu ubiquiti" >> /etc/apt/sources.list
apt-key adv --keyserver keyserver.ubuntu.com --recv 06E85760C0A52C50
apt-get update -y
apt-get install mfi -y --allow-unauthenticated
7. Visit https://<ip>:6443/wizard to configure your mFi Controller
